My first step is using a miter vise to make certain that I have a flush end.
Then I measure the thickness of the metal on the gauge and lock it into place with the knob.
Place the wire on the gauge for sizing.
I then use a wooden ring clamp to hold both the wire and gauge in place. This also frees up one hand to position the assembled pieces for easier sawing.
At the base of the gauge is a slot for you to saw.